Most Semprons are thoroughbred core Athlon XP's with different performance
ratings comparing them to Celerons rather than Pentium 4's. They have 256k
cache and run on a 333fsb. They should work in any Socket A board, but may
be mis-identified on older boards. Most should have bios updates available.
The Sempron 3100+ (1.8Ghz) is a Socket 754 part based on the Athlon 64, but
with the 64 bit capabilites disabled. It also has 256k cache and is a pretty
good performer for the money. That being said, the 333fsb barton core Athlon
XP's are a better value right now. I believe that the AMD is discontinuing
the Athlon XP at the end of the year.